vcl: reset OpenGLContext(s) when yielding the last SolarMutex.

This should make OpenGL thread-safe to allow multiple threads to
render using VCL's OpenGL backend, and fix misc. associated driver
horrors, will give some performance cost for tight Yield loops.

Change-Id: Ib23702262fd9f0925a5ed8c642d0a26e92136b37

include/vcl/opengl/OpenGLContext.hxx

@@ -199,8 +199,14 @@ public:
     OpenGLProgram*      UseProgram( const OUString& rVertexShader, const OUString& rFragmentShader );
 
     bool isCurrent();
-    void clearCurrent();
+    static void clearCurrent();
+    /// reset all contexts dis-associating them with their underlying
+    /// resources before a potential thread switch.
+    static void resetAllContexts();
+
+    /// make this GL context current - so it is implicit in subsequent GL calls
     void makeCurrent();
+    /// reset the GL context so this context is not implicit in subsequent GL calls.
     void resetCurrent();
     void swapBuffers();
     void sync();

vcl/generic/app/geninst.cxx

@@ -21,8 +21,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-#include "osl/module.hxx"
-#include "tools/solarmutex.hxx"
+#include <osl/module.hxx>
+#include <tools/solarmutex.hxx>
+#include <vcl/opengl/OpenGLContext.hxx>
 
 #include "generic/geninst.h"
 
@@ -53,7 +54,10 @@ void SalYieldMutex::release()
     if ( mnThreadId == osl::Thread::getCurrentIdentifier() )
     {
         if ( mnCount == 1 )
+        {
+            OpenGLContext::resetAllContexts();
             mnThreadId = 0;
+        }
         mnCount--;
     }
     m_mutex.release();

vcl/osx/salinst.cxx

@@ -31,6 +31,7 @@
 #include "vcl/window.hxx"
 #include "vcl/timer.hxx"
 #include "vcl/svmain.hxx"
+#include "vcl/opengl/OpenGLContext.hxx"
 
 #include "osx/saldata.hxx"
 #include "osx/salinst.h"
@@ -269,7 +270,10 @@ void SalYieldMutex::release()
     if ( mnThreadId == osl::Thread::getCurrentIdentifier() )
     {
         if ( mnCount == 1 )
+        {
+            OpenGLContext::resetAllContexts();
             mnThreadId = 0;
+        }
         mnCount--;
     }
     m_mutex.release();

vcl/source/opengl/OpenGLContext.cxx

@@ -82,6 +82,9 @@ OpenGLContext::OpenGLContext():
     else
         pSVData->maGDIData.mpFirstContext = this;
     pSVData->maGDIData.mpLastContext = this;
+
+    // FIXME: better hope we call 'makeCurrent' soon to preserve
+    // the invariant that the last item is the current context.
 }
 
 OpenGLContext::~OpenGLContext()
@@ -1289,6 +1292,22 @@ void OpenGLContext::clearCurrent()
         pCurrentCtx->ReleaseFramebuffers();
 }
 
+void OpenGLContext::resetAllContexts()
+{
+    ImplSVData* pSVData = ImplGetSVData();
+
+    // release all framebuffers from the old context so we can re-attach the
+    // texture in the new context
+    for (OpenGLContext* l = pSVData->maGDIData.mpLastContext; l;
+         l = l->mpPrevContext)
+    {
+        l->ReleaseFramebuffers();
+        if (l->isCurrent())
+            l->resetCurrent();
+        assert (!l->mpNextContext || l->mpNextContext->mpPrevContext == l);
+    }
+}
+
 void OpenGLContext::makeCurrent()
 {
     ImplSVData* pSVData = ImplGetSVData();
@@ -1318,7 +1337,7 @@ void OpenGLContext::makeCurrent()
     }
 #endif
 
-    // move the context at the end of the contexts list
+    // move the context to the end of the contexts list
     static int nSwitch = 0;
     SAL_INFO("vcl.opengl", "******* CONTEXT SWITCH " << ++nSwitch << " *********");
     if( mpNextContext )

vcl/win/source/app/salinst.cxx

@@ -28,6 +28,7 @@
 
 #include <vcl/apptypes.hxx>
 #include <vcl/opengl/OpenGLHelper.hxx>
+#include <vcl/opengl/OpenGLContext.hxx>
 #include <vcl/timer.hxx>
 
 #include <opengl/salbmp.hxx>
@@ -148,6 +149,8 @@ void SalYieldMutex::release()
         {
             if ( mnCount == 1 )
             {
+                OpenGLContext::resetAllContexts();
+
                 // If we don't call these message, the Output from the
                 // Java clients doesn't come in the right order
                 GdiFlush();